In recent years, a fuel cell has been used in a computer, a mobile phone, an automobile or the like. The fuel cell includes a stack which is obtained by stacking cells generating electric power by gas supplied from the outside. The cell includes electrolyte as well as a cathode and an anode facing each other through the electrolyte. The cell generates electric power by an electrical chemical reaction occurring when oxidation gas including oxygen such as air is supplied to a cathode and fuel gas including hydrogen is supplied to an anode.
In the anode, hydrogen is changed into hydrogen ions by a catalyst and hence electrons are generated. In order to reduce the wasted hydrogen in the fuel cell, fuel gas including unreacted hydrogen is circulated so as to be supplied to the anode again. In the cathode, water is produced by the reaction of the oxygen of the oxidation gas and the hydrogen ions passing through the electrolyte. The produced water is discharged to the outside of the fuel cell along with the unreacted oxidation gas.
Here, a part of the water produced in the cathode passes through the electrolyte inside the cell to move toward the anode, and is circulated inside the fuel cell along with the unreacted fuel gas to stay therein. The staying water disturbs the supply of hydrogen to the anode. Further, when air is used as the oxidation gas, a part of nitrogen in the air passes through the electrolyte to move toward the anode. The nitrogen moving toward the anode is circulated inside the fuel cell along with the fuel gas including unreacted hydrogen. An increase in nitrogen concentration inside the fuel cell causes a decrease in hydrogen concentration, and hence the performance of the cell is degraded.
Accordingly, in order to discharge the water and the nitrogen, the fuel cell includes a gas-liquid separator which is provided in a circulation line and a discharge valve which is connected to the gas-liquid separator. The gas-liquid separator separately stores the water and the gas therein. The water which is produced by the generation of electric power and stays inside the fuel cell is stored inside the gas-liquid separator by a predetermined amount and is discharged to the outside. Further, the nitrogen is discharged at the same time in such a manner that the discharge valve discharges a predetermined amount of the gas inside the gas-liquid separator after the water is discharged. The fuel cell discharges a desired amount of water and fuel gas by controlling the operation of the discharge valve.
When an abnormality such as a failure or a problem occurs in the discharge valve, there is a concern that the water and the gas inside the gas-liquid separator are not discharged and the performance of the fuel cell is degraded. Accordingly, there is a case where the fuel cell determines the abnormality of the discharge valve of the fuel cell. An example of the fuel cell includes two discharge valves connected in series to the gas-liquid separator. In the fuel cell, the abnormality of the opening and closing operations of two discharge valves is determined in such a manner that the operation time points of two discharge valves are set to be different in the gas discharge state and a pressure change between two discharge valves in the gas leakage state is detected by a pressure sensor.
However, in the fuel cell, since the abnormality of the opening and closing operations of the discharge valve is determined by a change in pressure caused by the leakage of the gas, a problem arises in that the fuel gas is uselessly discharged.
In consideration of the above-described circumstances, it is an object to provide an example embodiment of a fuel cell capable of determining the abnormality of a discharge valve without discharging gas inside a gas-liquid separator and an abnormality determination method.
According to one aspect of the example embodiment, the fuel cell includes a gas-liquid separator separately storing gas and water; a discharge valve discharging the gas and the water; a control unit controlling the operation of the discharge valve; and a detector detecting a water level of the gas-liquid separator. The control unit is configured to determine an abnormality of the discharge valve based on a change in the water level caused by opening and closing of the discharge valve if the water level detected by the detector is equal to or higher than a first threshold.
According to one aspect of the example embodiment, the fuel cell includes a gas-liquid separator separately storing gas and water; a plurality of discharge valves discharging the gas and the water; a control unit controlling the operation of the discharge valves; a detector detecting a water level of the gas-liquid separator; and a clocking unit measuring an elapsed time from a time point when the gas and the water are discharged. The control unit is configured to determine an abnormality of the discharge valves if the detector detects a water level of a threshold or less after the clocking unit measures a predetermined time.
According to one aspect of the example embodiment, the abnormality determination method for determining an abnormality of a discharge valve of a fuel cell including a gas-liquid separator separately storing gas and water, a detector detecting a water level of the gas-liquid separator, a plurality of discharge valves disposed in series to discharge the gas and the water, and a control unit controlling operations of the discharge valves, comprises: determining whether the water level detected by the detector is equal to or higher than a threshold; and determining an abnormality of the discharge valves based on a change in the water level caused by an operation where the control unit opens and closes the discharge valves if determining the water level detected by the detector is equal to or higher than the threshold.
According to the example embodiment, it is possible to determine the abnormality of the discharge valve without discharging the gas inside the gas-liquid separator.
The above and further objects and features will more fully be apparent from the following detailed description with reference to the accompanying drawings.